Semiconductor device manufacturing method

1. A semiconductor device manufacturing method comprising: a first step in which, on a first main surface and a second main surface, which is a surface opposite to the first main surface of a semiconductor substrate, phosphorous is implanted in the second main surface by using multiple ion implantations of different acceleration energies so as to form a first impurity region on the semiconductor substrate; a second step in which a second conductivity-type impurity is implanted in the second main surface using an acceleration energy lower than the multiple ion implantations, and a second impurity region is formed so that a non-implantation region in which the impurity is not implanted is left between that and the first impurity region in the semiconductor substrate; a heat treatment step in which heat treatment is applied to the semiconductor substrate so that a buffer layer is formed by the phosphorous, a collector layer is formed by the second conductivity-type impurity, and a non-diffusion region in which the phosphorous and the second conductivity-type impurity do not diffuse is left between the buffer layer and the collector layer; and a step in which a collector electrode in contact with the collector layer is formed.

2. The semiconductor device manufacturing method according to claim 1 , wherein the phosphorous is implanted in the second main surface at the acceleration energy of 1 to 10 MeV; and the second conductivity-type impurity is implanted in the second main surface at the acceleration energy of 5 to 100 KeV.

3. The semiconductor device manufacturing method according to claim 1 , wherein dosages of the multiple ion implantations are uniform.

4. A semiconductor device manufacturing method comprising: a first step in which, on a first main surface and a second main surface, which is a surface opposite to the first main surface of a semiconductor substrate, a first conductivity-type impurity is implanted in the second main surface by using multiple ion implantations of different acceleration energies so as to form a first impurity region on the semiconductor substrate; a second step in which a second conductivity-type impurity is implanted in the second main surface using an acceleration energy lower than the multiple ion implantations, and a second impurity region is formed so that a non-implantation region in which the impurity is not implanted is left between that and the first impurity region in the semiconductor substrate; a heat treatment step in which a heat treatment is applied to the semiconductor substrate so that a buffer layer is formed by the first conductivity-type impurity, a collector layer is formed by the second conductivity-type impurity, and a non-diffusion region in which the first conductivity-type impurity and the second conductivity-type impurity do not diffuse is left between the buffer layer and the collector layer; and a step in which a collector electrode in contact with the collector layer is formed, wherein the multiple ion implantations are performed so that the dosage of the first conductivity-type impurity becomes larger as going closer to the second main surface side, and the impurity concentration profile of the buffer layer has only a single peak.

5. The semiconductor device manufacturing method according to claim 4 , wherein in the first step, the first conductivity-type impurity is implanted perpendicularly to the second main surface.

6. A semiconductor device manufacturing method comprising: a first step in which, on a first main surface and a second main surface, which is a surface opposite to the first main surface of a semiconductor substrate, a first conductivity-type impurity is implanted in the second main surface by using multiple ion implantations of different acceleration energies so as to form a first impurity region on the semiconductor substrate; a second step in which a second conductivity-type impurity is implanted in the second main surface using an acceleration energy lower than the multiple ion implantations, and a second impurity region is formed so that a non-implantation region, in which the impurity is not implanted, is left between that the first impurity region in the semiconductor substrate; a single heat treatment step in which a heat treatment is applied to the semiconductor substrate to form a buffer layer by the first conductivity-type impurity, a collector layer by the second conductivity-type impurity, and a non-diffusion region in which the first conductivity-type impurity and the second conductivity-type impurity do not diffuse is left between the buffer layer and the collector layer, and a step in which a collector electrode in contact with the collector layer is formed.